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Model under-representation of decadal Pacific trade wind trends and its link to tropical Atlantic bias

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Kajtar, JB, Santoso, A, McGregor, S, England, MH and Baillie, Z 2018 , 'Model under-representation of decadal Pacific trade wind trends and its link to tropical Atlantic bias' , Climate Dynamics, vol. 50, no. 3-4 , 1471–1484 , doi: 10.1007/s00382-017-3699-5.

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Abstract

The strengthening of the Pacific trade winds in recent decades has been unmatched in the observational record stretching back to the early twentieth century. This wind strengthening has been connected with numerous climate-related phenomena, including accelerated sea-level rise in the western Pacific, alterations to Indo-Pacific ocean currents, increased ocean heat uptake, and a slow-down in the rate of global-mean surface warming. Here we show that models in the Coupled Model Intercomparison Project phase 5 underestimate the observed range of decadal trends in the Pacific trade winds, despite capturing the range in decadal sea surface temperature (SST) variability. Analysis of observational data suggests that tropical Atlantic SST contributes considerably to the Pacific trade wind trends, whereas the Atlantic feedback in coupled models is muted. Atmosphere-only simulations forced by observed SST are capable of recovering the time-variation and the magnitude of the trade wind trends. Hence, we explore whether it is the biases in the mean or in the anomalous SST patterns that are responsible for the under-representation in fully coupled models. Over interannual time-scales, we find that model biases in the patterns of Atlantic SST anomalies are the strongest source of error in the precipitation and atmospheric circulation response. In contrast, on decadal time-scales, the magnitude of the model biases in Atlantic mean SST are directly linked with the trade wind variability response.

Item Type: Article
Authors/Creators:Kajtar, JB and Santoso, A and McGregor, S and England, MH and Baillie, Z
Keywords: CMIP5, model biases, Pacific Ocean, Atlantic Ocean, trade winds, decadal variability, Walker circulation
Journal or Publication Title: Climate Dynamics
Publisher: Springer-Verlag
ISSN: 0930-7575
DOI / ID Number: 10.1007/s00382-017-3699-5
Copyright Information:

Copyright 2017 Springer-Verlag Berlin Heidelberg. This is a post-peer-review, pre-copyedit version of an article published in Climate Dynamics. The final authenticated version is available online at: http://dx.doi.org/10.1007/s00382-017-3699-5

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